The first thing that pops out here is the poor fuel economy, it could/should be around 30. As to the matter of my opinion to the fix it/buy a new car issue, I would take some other factors into consideration first. You already own this one, insurance costs, fuel economy(if it comes up to where it really should be)cost per year for maintaining the car, the safety of the car compared to a smaller vehicle and so forth. If money is the major factor here, then reselling the BMW would also need to be considered. Having these issues on the table now can change the conversation, what is your take?

Actually, my 530 is quite capable of pulling 24-25 MPGs highway, the problem is ME! I'm not capable of driving under 80MPH! LOL!

Seriously though, I do need to crunch the numbers to see where everything lies. My commute is 95% flat highway. With gas prices skyrocketing (again!) MPGs is becoming a greater concern. Reselling this car could also prove difficult as well.